Carrier 50VZ Installation, Operation And Maintenance Instructions

Also see for 38PZ: Installation manual Installation manual

Carrier 50VZ Installation, Operation And Maintenance Instructions Manual pdf 31 page image

31- Check the drain connections.- Ensure that there are no refrigerant leaks.- Confirm that the electrical power source agrees with theunit nameplate rating.- Make sure that compressors float freely on the mountingsprings.WARNING: The compressors are mounted on vibrationisolators. Do not loosen or remove the support mounting bolts.- Check for proper fan rotation.Refrigerant chargeGas tightness testing and dehydration50VZ/PZ units are shipped fully charged with refrigerant R-407Cready for operation. If, when the unit is run, symptoms of lossof charge (for example, low pressure switch tripping orabnormally low cooling capacities) are detected, first conduct aleak test followed, if necessary, by a gas tightness test usingcompressed nitrogen. For the latter all refrigerant must beremoved from the circuit. Transfer the refrigerant to a storagetank and then rinse the circuit. For your information, we arelisting here some precautions that need to be taken intoconsideration, when working with these units.Refrigerant guidelines for R-407CRefrigerant R-407C consists of a non-azeotropic blend of 23%of R-32, 25% of R-125 and 52% of R-134a, and is character-ised by the fact that at the time of the change in state thetemperature of the liquid/vapour mixture is not constant. Allchecks must be pressure tests, and the appropriate pressure/temperature ratio table must be used for the interpretation ofthe values.Leak detection is especially important for units charged withrefigerant R-407C. Depending on whether the leak occurs inthe liquid or the vapour phase, the proportion of the differentcomponents in the mixture remaining in the unit is not thesame.The following basic guidelines must be observed:• Leaks must be repaired immediately by qualifiedpersonnel.• Refrigerant must never be discharged to the atmosphere.• Use a refrigerant reclaim unit.• Any loss of oil from the system during maintenance mustbe stopped immediately and the collected oil must byremoved in accordance with applicable regulations38VZ/PZ and 40PZ units are supplied with a nitrogen holdingcharge. This must be removed before soldering the connectingrefrigerant lines to the unit. Once the soldering has beencompleted, the complete refrigerant circuit must be evacuatedthen the correct quantity of R-407C refrigerant for each systemmust be charged.WARNING: If any brazing is to be done the refrigerant circuitmust be filled with nitrogen. Combustion of refrigerantproduces toxic phosgene gas.VERY IMPORTANT:- Never use the compressor as a vacuum pump.- If more refrigerant is needed add gas very slowly via thesuction line. Liquid refrigerant must never be introducedinto the suction line.- Do not overcharge with refrigerant.START-UPActual start-up should only be done under the supervision of aqualified refrigeration mechanic. These units include theMaster Link II electronic control. The operation of the controlis explained in the instructions accompanying each unit.Initial checksWith the unit in operation, ensure that the values shown on thehigh and low pressure gauges are within the normal limits. It isadvisable to simulate unit shutdown due to high and lowpressure, in order to make sure that the pressurestats workproperly. To do so, proceed as follows:- High pressure shutdown: Completely cover the outdoorair inlet, or disconnect the outdoor fan and motor. Theunit should stop at a pressure of 2844 kPa.- Low pressure shutdown: Cover the indoor air inlet, or dis-connect the indoor fan and motor. Observe the low pressuregauge. The unit should stop at a pressure of 265 kPa.In both cases, after a reasonable time, reset the unit through theremote control as previously indicated.Check that the motor and compressor consumptions areapproximately the same as those shown on the unit nameplate.Consumption data is also given in Table 2.Refrigerant system descriptionThe refrigerant circuit incorporates the following primaryelements:- Refrigerant-air heat exchanger: made of high qualitycopper tubes and pretreated aluminium fins, for extracorrosion resistance and greater protection than offered bycopper fins.- Refrigerant lines: made completely of high qualitycopper.- Expansion valve or metering device.- Compressors: hermetic reciprocating or scrollcompressors depending on model, cooled by suction gas.They incorporate internal protection.- Filter drier and Schrader valves.- Safety elements: high, low pressurestat.- All units are supplied with the correct refrigerant charge.- The split system units are supplied with a nitrogenholding charge which must be evacuated and replacedwith the right refrigerant charge for the unit size and theconnection lines.Compressor replacementWhen an internal fault occurs, the compressor must bereplaced. This must be done as detailed below:- Disconnect the unit from the electrical supply.- Remove the panels.